This invention relates to a method for obtaining trigger signals to regulate the energy conversion in the combustion chamber of an internal combustion engine.
Injection of fuel into a combustion chamber of an internal combustion engine is effected by providing individual injection valves for each combustion chamber which inject controlled quantities of fuel either directly into the combustion chamber itself or into an intake duct leading to the combustion chamber. Methods for regulating the energy conversion in each combustion chamber as a function of its share in the power output of the engine are disclosed, for example, in German Offenlegungsschrift No. 38 02 803, Published European Patent Application No. 113,227 and German Offenlegungsschrift No. 38 21 740. The share of the power output to be provided by each combustion chamber may be determined in various ways, for example, by determining engine roughness, measuring engine torque reactions, evaluating sound conducted from the engine by an acoustic sensor, measuring the exhaust temperature, measuring the injection pressure by a pressure sensor, or measuring the progress of combustion by an ionic flux sensor in each combustion chamber.
Regardless of whether signals for fuel injection and for regulation of energy conversion are obtained individually for each combustion chamber or whether signals are obtained which apply to all combustion chambers, the acquisition of the fuel injection signals and the trigger signals to regulate energy conversion and the regulation to particular injection and ignition times are independent of each other.
It has been found, however, that, in modern engine design, especially in internal combustion engines for motor vehicles, the difference between the commencement of injection and the triggering of ignition measured in units of time or in crankshaft angle, and the proportioning of fuel as a function of engine speed, are often more important than a definite coordination with the top dead center position of the piston or a specific crankshaft angle.
The problem of regulating energy conversion is aggravated by the fact that dimensional variations resulting from production tolerances or wear, especially with respect to the injection valve, may produce operational variations which are disadvantageous with respect to precision of the combustion timing. In mass production, as is well known, extensive testing operations involving a substantial expense are carried out on injection valves in order to achieve low dimensional variations.